These are just rumors, to be sure, and have been circulating at some level for almost a year.
SAP has strongly denied the rumors during that time, though chairman Hasso Plattner unintentionally put some fuel in the fire last May by saying to the German Financial Times last year that: “There are only three potential buyers [of SAP]: IBM, Microsoft and Google. Of all companies, I don’t see anyone else. If shareholders think that a combination, and not independence, is better, then it will happen.”

From the services model that IBM follows, it makes sense to acquire a behemoth like SAP purely for its installed base and then sell all sorts of services to them. But the larger question is – what’s the room for growth here? From a software sales point of view, the market is pretty much saturated. My own view of the ERP behemoth is that given the utter complexity of something of the order of SAP/Oracle and the implicit insistence that the firm adapt to SAP’s version of reality – there is quite an opportunity for an intelligent class of enterprise software to make deep inroads.
Whatever the big honchos at IBM are thinking, I’m skeptical of such a merger simply because of revenues from any sort of installed base growth. The market space where there is some growth potential seems to be:

IBM and SAP have an existing partnership to bring ERP to the small and mid-sized company market. Penetrating these smaller companies has been a key marketing goal of SAP for the past few years.

The question is – why pick an elephant (or a sheared down version of an elephant) to run what needs to be, strategically and execution-wise, a nimble organization? Any new entrant in the enterprise software space needs to enter via the small and mid-sized company market because that’s where the behemoths are concentrating their efforts.
Old Chinese (Confucius) saying: “Do not use a cannon to kill a mosquito.”
This makes for an exciting few years ahead.